The present invention relates to a boom element for a telescopic boom, in particular to a telescopic section or to a pivotal connection piece of a telescopic boom, to a telescopic boom, to a pinning system and to a construction vehicle.
In wind power plants, very large hub heights are in the meantime being sought for the wind turbines to obtain a wind power on the rotor blades which is as homogenous as possible. In the assembly of wind power plants, the maximum achievable hub height therefore represents a characteristic value for the required hoisting units, usually mobile cranes having telescopic booms.
Starting from the demand of providing very large boom systems with a large boom length, the problem has occurred that customary telescopic booms have become too heavy. Telescopic booms, however, have the advantage over booms made from customary lattice elements that they can be switched fast from a transport state to a working state and take up substantially less room in the assembly. A further substantial advantage comprises the fact that, with the usually used lattice mast cranes, derrick booms are required for erecting the boom using corresponding derrick ballast for the assembly of the wind power plants with the large boom lengths.
Furthermore, when a crane having a lattice boom is moved on a construction site in the erected state, i.e. should change its location, the total center of gravity of the crane is very high. If the lattice boom could be telescoped inward, it would not be necessary to set up the boom with a very steep angle to achieve a required security with respect to the risk of tipping over. A lower center of gravity could namely be achieved by the telescoping inward, which has very great advantages with respect to the risk of tipping over.
A telescopic boom having telescopic sections is already known from DE 200 14 056 U1 in which the corner sections of the telescopic section are connected to one another by means of lattice bars arranged in a half-timbered manner and by means of connection plates.
Furthermore, a multi-section telescopic system is known from EP 0 754 646 A1 in which the telescopic sections can be pinned for the purpose of locking by means of a pinning system.